Golf ball which includes fast-chemical-reaction-produced component and method of making same

ABSTRACT

Disclosed herein is a golf ball having a cover composed of a transparent reaction injection molded polyurethane material. The cover is transparent to visible light and allows for viewing of a core or boundary layer. The core or boundary layer may have a visually appealing color. Further, an indicia may be printed on a surface of the core or boundary layer, and the indicia is visible through the cover material.

CROSS REFERENCES TO RELATED APPLICATIONS

The Present Application is a continuation application of U.S. patentapplication Ser. No. 11/193,933, filed Jul. 29, 2005 now U.S. Pat. No.7,160,210, which is a continuation-in-part application of U.S. patentapplication Ser. No. 10/905,913, filed on Jan. 26, 2005, which is acontinuation-in-part application of U.S. patent application Ser. No.09/040,798, filed Mar. 18, 1998, now U.S. Pat. No. 6,855,073 and acontinuation-in-part application of U.S. patent application Ser. No.09/877,600 filed Jun. 8, 2001 now U.S. Pat. No. 6,905,424, which is acontinuation-in-part application of U.S. patent application Ser. No.09/411,690, filed Oct. 1, 1999, now U.S. Pat. No. 6,290,614, which is acontinuation-in-part application of U.S. patent application Ser. No.09/040,798 filed Mar. 18, 1998, now U.S. Pat. No. 6,855,073.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates generally to golf balls, and more particularly togolf balls that contain a fast-chemical-reaction-produced component,such as a core and/or cover layer.

2. Description of the Related Art

Golf balls comprise, in general, three types. The first type is amulti-piece wound ball wherein a vulcanized rubber thread is wound undertension around a solid or semi-solid core, and thereafter enclosed in asingle or multi-layer covering of a tough, protective material. A secondtype of a golf ball is a one-piece ball formed from a solid mass ofresilient material that has been cured to develop the necessary degreeof hardness to provide utility. One-piece molded balls do not have asecond enclosing cover. A third type of ball is a multi-piece non-woundball which includes a liquid, gel or solid core of one or more layersand a cover having one or more layers formed over the core.

Conventional golf ball covers have been made of ionomer, balata, andslow-reacting, thermoset polyurethane. When polyurethane covers are madeby conventional methods, such as by casting, a substantial amount oftime and energy are required, thus resulting in relatively high cost.

It would be useful to develop a golf ball containing afast-chemical-reaction-produced component, such as at least one core orcover layer, particularly one which contains polyurethane, polyurea,epoxy and/or unsaturated polyester, and which has excellent lightstability and physical properties.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to produce a golf ball having apolyurethane cover which is formed by a fast chemical reaction. The golfball cover comprises a light stable, aliphatic-based polyurethanecomponent which is formed by reaction injection molding. The golf ballhas physical properties, such as scuff and cut resistance, that arecomparable to aromatic-based polyurethane covers. Further, the covermaterial is transparent to visible light.

A preferred form of the invention is a multi-piece golf ball having acover layer comprising a reaction injection molded material comprisingpolyurethane/polyurea. The reaction injection molded material ispreferably an aliphatic-based material. The golf ball cover preferablyhas a Shore B hardness in the range of from about 20 to about 95, morepreferably from about 30 to about 75, and a flex modulus in the range of1 to about 310 kpsi, and more preferably from about 5 to about 100 kpsi.The golf ball has improved scuff and cut resistance and superior lightfastness and weathering over golf ball covers comprising aromatic basedpolyurethane/polyurea materials.

The golf ball of the invention can include, in the boundary layer,optical brighteners, white pigment, UV stabilizers, antioxidants, andother materials. The boundary layer may be formed to have a colorselected from the group consisting of blue, red, white, green, yellow,orange, black, brown, pink, grey and purple, and the color of theboundary layer is visible through the cover.

Having briefly described the present invention, the above and furtherobjects, features and advantages thereof will be recognized by thoseskilled in the pertinent art from the following detailed description ofthe invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a first embodiment of a golf ball having a cover formedaccording to a reaction injection molded (RIM) process.

FIG. 2 is a second embodiment of a golf ball formed according to areaction injection molded (RIM) process.

FIG. 3 is a third embodiment of a golf ball formed according to areaction injection molded (RIM) process.

FIG. 4 is a process flow diagram which schematically depicts a reactioninjection molding process.

FIG. 5 schematically shows a mold for reaction injection molding a golfball cover.

DETAILED DESCRIPTION OF THE INVENTION

A golf ball cover layer formed according to the invention is transparentto visible light. The cover layer preferably preferably has a flexmodulus in the range of from about 1 to about 310 kpsi, a Shore Bhardness in the range of from about 20 to about 95, and good lightfastness and weathering, good scuff resistance and good cut resistance.As used herein, “polyurethane and/or polyurea” is expressed as“polyurethane/polyurea”.

Reaction injection molding covers for golf balls offers numerousadvantages over conventional slow-reactive processes for producing golfball covers. The RIM process produces molded covers in a mold release ordemold time of 10 minutes or less, preferably 2 minutes or less, andmost preferably in 1 minute or less. The RIM: process also results inthe formation of a reaction product, formed by mixing two or morereactants together, that exhibits a reaction time of about 2 minutes orless, preferably 1 minute or less, more preferably 30 seconds or less,and most preferably about 15 seconds or less. An excellent finish canalso be produced on the ball.

The term “demold time” generally refers to the mold release time, whichis the time span from the mixing of the components until the earliestpossible time at which the part may be removed from the mold. At thattime of removal, the part is said to exhibit sufficient “greenstrength”. The term “reaction time” generally refers to the setting timeor curing time, which is the time span from the beginning of mixinguntil the time at which the product no longer flows. Further descriptionof the terms setting time and mold release time are provided in thePolyurethane Handbook, edited by Günter Oertel, Second Edition, ISBN1-56990-157-0, herein incorporated by reference.

The RIM process is particularly effective when recycled polyurethane orother polymer resin, or materials derived by recycling polyurethane orother polymer resin, are incorporated into the product. The process mayinclude the step of recycling at least a portion of the reactionproduct, preferably by glycolysis. From about 5% to about 100% of thepolyurethane/polyurea formed from the reactants used to form particularcomponents can be obtained from recycled polyurethane/polyurea.

The preferred method of forming a fast-chemical-reaction-producedcomponent for a golf ball according to the invention is by reactioninjection molding (RIM). RIM is a process by which highly reactiveliquids are injected into a closed mold, mixed usually by impingementand/or mechanical mixing in an in-line device such as a “peanut mixer”,where they polymerize primarily in the mold to form a coherent,one-piece molded article. The RIM processes usually involve a rapidreaction between one or more reactive components such as polyether- orpolyester-polyol, polyamine, or other material with an active hydrogen,and one or more isocyanate—containing constituents, often in thepresence of a catalyst. The constituents are stored in separate tanksprior to molding and may be first mixed in a mix head upstream of a moldand then injected into the mold. The liquid streams are metered in thedesired weight to weight ratio and fed into an impingement mix head,with mixing occurring under high pressure (for example, at about 1500 toabout 3000 psi). The liquid streams impinge upon each other in themixing chamber of the mix head and the mixture is injected into themold. One of the liquid streams typically contains a catalyst for thereaction. The constituents react rapidly after mixing to gel and formpolyurethane polymers. Polyureas, epoxies, and various unsaturatedpolyesters also can be molded by RIM.

RIM differs from non-reaction injection molding in a number of ways. Themain distinction is that in RIM a chemical reaction takes place in themold to transform a monomer or adducts to polymers and the componentsare in liquid form. Thus, a RIM mold need not be made to withstand thepressures which occur in a conventional injection molding. In contrast,injection molding is conducted at high molding pressures in the moldcavity by melting a solid resin and conveying it into a mold, with themolten resin often being at about 150 to about 350° C. At this elevatedtemperature, the viscosity of the molten resin usually is in the rangeof about 50,000 to about 1,000,000 centipoise, and is typically around200,000 centipoise. In an injection molding process, the solidificationof the resins occurs after about 10-90 seconds, depending upon the sizeof the molded product, the temperature and heat transfer conditions, andthe hardness of the injection molded material. Subsequently, the moldedproduct is removed from the mold. There is no significant chemicalreaction taking place in an injection molding process when thethermoplastic resin is introduced into the mold. In contrast, in a RIMprocess, the chemical reaction typically takes place in less than abouttwo minutes, preferably in under one minute, and in many cases in about30 seconds or less.

If plastic products are produced by combining components that arepreformed to some extent, subsequent failure can occur at a location onthe cover which is along the seam or parting line of the mold. Failurecan occur at this location because this interfacial region isintrinsically different from the remainder of the cover layer and can beweaker or more stressed. The present invention is believed to providefor improved durability of a golf ball cover layer by providing auniform or “seamless” cover in which the properties of the covermaterial in the region along the parting line are generally the same asthe properties of the cover material at other locations on the cover,including at the poles. The improvement in durability is believed to bea result of the fact that the reaction mixture is distributed uniformlyinto a closed mold. This uniform distribution of the injected materialssignificantly reduces and/or eliminates knit-lines and other moldingdeficiencies which can be caused by temperature difference and/orreaction difference in the injected materials. The process of theinvention results in generally uniform molecular structure, density andstress distribution as compared to conventional injection-moldingprocesses.

Catalysts can be added to the RIM polyurethane system starting materialsas long as the catalysts generally do not react with the constituentwith which they are combined. Suitable catalysts include those that areknown to be useful with polyurethanes and polyureas. Examples ofcatalysts are those well known in the art of polyurethanes, such as tin,zinc and zirconium catalysts, as well as amine catalysts. The tin, zincor zirconium catalyst preferably comprises at least one member selectedfrom the group consisting of a zirconium complex, dibutyl tin dilaurate,dibutyl acetylacetonate, dibutyl tin dibutoxide, dibutyl tin sulphide,dibutyl tin di-2-ethylhexanoate, dibutyl tin (IV) diacetate, dialkyltin(IV) oxide, tributyl tin laurylmercaptate, dibutyl tin dichloride,organo lead, tetrabutyl titanate, tertiary amines, mercaptides, stannousoctoate, potassium octoate, zinc octoate, diaza compounds, and potassiumacetate. Examples of amine catalysts include, but are not limited to,N,N,N′-trimethyl-N-hydroxyethyl-bisaminoethyl ether; N,N-bis(3-dimethylaminopropyl)-N-isopropanol amine;N-(3-dimethylaminopropyl)-N,N-diisopropanolamine;N,N-dimethylethanolamine; and 2-(2-dimethylaminoethoxy) ethanol. Thequantity of catalyst will depend upon the type of catalyst, polyol, andpolyisocyanate used, as well as the curing temperature and desiredcuring time and other factors. Generally, the amount of catalyst used isfrom about 0.005 to 0.5 weight percent. Two or more different catalystsmay also be used if desired.

The reaction mixture viscosity should be sufficiently low to ensure thatthe empty space in the mold is completely filled. The reactant materialsgenerally are preheated to about 80 to 200° F. before they are mixed. Inmost cases it is necessary to preheat the mold, for example, to about 80to 200° F., to ensure proper injection viscosity.

Referring now to the drawings, and first to FIG. 1, a golf ball having acover comprising a RIM polyurethane is shown. The golf ball 10 includesa core 12 and a polyurethane cover 14 formed by RIM. The polyurethanecover 14 is transparent to visible light and a surface of the core 12 isvisible. An indicia, such as a logo, may be printed on the surface ofthe core 12. Further, the core 12 may be formed to have a color selectedfrom the group of blue, red, white, green, yellow, orange, black, brown,pink, grey, purple or any other color. The color of the core 12 isvisible through the cover 14.

Referring now to FIG. 2, a golf ball having a core comprising a RIMpolyurethane is shown. The golf ball 20 has a RIM polyurethane core 22,and a RIM polyurethane cover 24. The RIM polyurethane cover 24 istransparent to visible light and a surface of the RIM polyurethane core22 is visible. An indicia, such as a logo, may be printed on the surfaceof the RIM polyurethane core 22.

Referring to FIG. 3, a multi-layer golf ball 30 is shown with a core 32,a boundary layer 34, and a cover layer 36 comprising a RIM polyurethanematerial. The core 32 and/or boundary layer 34 may comprise RIMpolyurethane or any other material known in the golf ball art. Thepolyurethane cover 36 is transparent to visible light and a surface ofthe boundary layer 34 is visible. An indicia, such as a logo, may beprinted on the surface of the boundary layer 34. Further, the boundarylayer 34 may be formed to have a color selected from the group of blue,red, white, green, yellow, orange, black, brown, pink, grey, purple orany other color. The color of the boundary layer 34 is visible throughthe cover 36.

Referring next to FIG. 4, a process flow diagram for a preferred processfor forming a RIM cover of polyurethane is shown. Isocyanate from bulkstorage is fed through line 80 to an isocyanate tank 100. The isocyanateis heated to the desired temperature, for example, to about 80 to about200° F., by circulating it through heat exchanger 82 via lines 84 and86. Polyol, polyamine, or another compound with an active hydrogen atomis conveyed from bulk storage to a polyol tank 108 via line 88. Thepolyol is heated to the desired temperature, for example, to about 80 toabout 200° F., by circulating it through heat exchanger 90 via lines 92and 94. Dry nitrogen gas is fed from nitrogen tank 96 to isocyanate tank100 via line 97 and to polyol tank 108 via line 98. Isocyanate is fedfrom isocyanate tank 100 via line 102 through a metering cylinder ormetering pump 104 into recirculation mix head inlet line 106. Polyol isfed from polyol tank 108 via line 110 through a metering cylinder ormetering pump 112 into a recirculation mix head inlet line 114. Therecirculation mix head 116 receives isocyanate and polyol, mixes them,and provides for them to be fed through nozzle 118 into injection mold120. The injection mold 120 has a top mold 122 and a bottom mold 124.Coolant flows through cooling lines 126 in the top mold 122 and lines128 in the bottom mold 124. The materials are kept under controlledtemperature conditions to insure that the desired reaction profile ismaintained.

The polyol component typically contains additives, such as stabilizers,flow modifiers, catalysts, combustion modifiers, blowing agents,fillers, pigments, surfactants, optical brighteners, and release agentsto modify physical characteristics of the cover. Recycledpolyurethane/polyurea also can be added to the core.Polyurethane/polyurea constituent molecules that were derived fromrecycled polyurethane can be added in the polyol component.

Inside the mix head, injector nozzles impinge the isocyanate and polyolat ultra-high velocity to provide excellent mixing. Additional mixingpreferably is conducted using an aftermixer 130, which typically isconstructed inside the mold between the mix head and the mold cavity.

As is shown in FIG. 5, the mold preferably includes a golf ball cavitychamber 132 in which a spherical golf ball mold 134 with a dimpled,spherical mold cavity 136 is positioned. The aftermixer 130 can be apeanut aftermixer, as is shown in FIG. 5, or in some cases anothersuitable type, such as a heart, harp or dipper. An overflow channel 138receives overflow material from the golf ball mold 134 through a shallowvent 136. Cooling water passages 138, which preferably are in a parallelflow arrangement, carry cooling water through the top mold 122 and thebottom mold 124.

The mold cavity is preferably constructed such as disclosed in U.S. Pat.No. 6,699,027 for Molding Processes And Apparatuses For Forming GolfBalls, which pertinent parts are hereby incorporated by reference.Alternatively, the mold cavity contains retractable pins and isgenerally constructed in the same manner as a mold cavity used toinjection mold a thermoplastic, e.g., ionomeric golf ball cover.However, a few differences when RIM is used are that tighter pintolerances generally are required, a lower mold temperature is used, anda lower injection pressure is used. Also, the molds can be produced fromlower strength material such as aluminum.

The golf balls formed according to the present invention can be coatedusing a conventional two-component spray coating or can be coated duringthe RIM process, for example, by using an in-mold coating process.

One of the significant advantages of the RIM process according to theinvention is that polyurethane or other cover material can be recycledand used in golf ball cores. Recycling can be conducted by, for example,glycolysis. Typically, about 10 to 80% of the material which isinjection molded actually becomes part of the cover. The remaining 20 to90% is recycled.

Recycling of polyurethanes by glycolysis is known from, for example, RIMPart and Mold Design—Polyurethanes, 1995, Bayer Corp., Pittsburgh, Pa.Another significant advantage of the present invention is that becausereaction injection molding occurs at low temperatures and pressures (forexample, about 80 to about 200° F. and about 100 to 200 psi), thisprocess is particularly beneficial when a cover is to be molded over avery soft core. When higher pressures are used for molding over softcores, the cores “shut off” or deform and impede the flow of materialcausing uneven distribution of cover material.

Polyisocyanates represent the key substances in formingpolyurethane/polyurea. The general structure of polyisocyanates isR—(NCO)_(n), where n is at least two, and R is an aromatic or analiphatic group. The isocyanate groups (—N═C═O) that react with hydroxylgroups form a polyurethane, whereas isocyanate groups that react with anamine group form a polyurea. In the present invention, the isocyanategroups (i.e., the “iso” side) may react with the hydroxyl group, theamine group, or both (i.e., the “polyol” side), in order to formpolyurethane/polyurea.

In a preferred embodiment, the polyurethane component which of thepresent invention incorporates an aliphatic isocyanate or isocyanateprepolymer. Aliphatic isocyanates include, but are not limited to,hexamethylene diisocyanate (HDI); Methylene Dicyclohexyl Diisocyanate(H₁₂MDI); isophorone diisocyanate (IPDI); tetramethylene diisocyanate;octamethylene diisocyanate; decamethylene diisocyanate; dodecamethylenediisocyanate; tetradecamethylene diisocyanate; derivatives of lysinediisocyanate (LDI); tetramethylxylylene diisocyanate; trimethylhexanediisocyanate (TMDI) or tetramethylhexane diisocyanate; cycloaliphaticdiisocyanates such as 1,4-, 1,3- or 1,2-diisocyanatocyclohexane;4,4-di(isocyanatocyclohexyl)methane;1-isocyanato-3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexane-(isophorone diisocyanate); 1,5-naphthalenediisocyanate (NDI)or 2,4- or 2,6-diisocyanator-1-methylcyclohexane. Aliphatic isocyanatesgenerally exhibit good light fastness and UV stability, but are slowerto react and produce softer polymers than the aromatic isocyanates.Polyurethanes based on an aliphatic diisocyanate can provide improvedgloss retention UV light stability, thermal stability hydrolyticstability. Additionally, TMXDI (META) aliphatic isocyanate hasdemonstrated favorable toxicological properties. Furthermore, because ithas a low viscosity, it is usable with a wider range of diols (topolyurethane) and diamines (to polyureas). If TMXDI is used, ittypically, but not necessarily, is added as a direct replacement forsome or all of the other aliphatic isocyanates in accordance with thesuggestions of the supplier. Because of slow reactivity of TMXDI, it maybe useful or necessary to use catalysts to have practical demoldingtimes. Hardness, tensile strength and elongation can be adjusted byadding further materials in accordance with the supplier's instructions.IPDI is preferred in some cases due to its good impact resistance.

The polyol component is preferably a polyester or polyether basedprepolymer. Examples of polyester and polyether based prepolymersinclude, but are not limited to, PTMEG; PPG; PEG; and the like. Apreferred polyol is PTMEG, but the polyol choice depends on the desiredfinal properties, such as scuff and cut resistance.

The polyol component typically contains additives, such as stabilizers,flow modifiers, catalysts, combustion modifiers, blowing agents,fillers, pigments, optical brighteners, and release agents to modifyphysical characteristics of the cover. Polyurethane/polyurea constituentmolecules that were derived from recycled polyurethane can be added inthe polyol component.

Chain extenders may also be used with polyisocyanates to formpolyurethane/polyurea. Chain extenders lengthen the main chain ofpolyurethane/polyurea causing end-to-end attachments. Examples of chainextenders for use in forming polyurethane/polyurea include glycol chainextenders and amine chain extenders. Suitable glycol chain extendersinclude, but are not limited to, ethylene glycol; propylene glycol;butane glycol; pentane glycol; hexane glycol; benzene glycol; xyleneglycol; 1,4-butane diol; 1,3-butane diol; 2,3-dimethyl-2,3-butane diol;and dipropylene glycol. Suitable amine chain extenders include, but arenot limited to, tetramethyl-ethylenediamine; dimethylbenzylamine;diethylbenzylamine; pentamethyldiethylenetriamine; dimethylcyclohexylamine; tetramethyl-1,3-butanediamine; 1,2-dimethylimidazole;bis-(dimethylaminoethylether); 2-methylimidazole; andpentamethyldipropylenetriamine.

Golf ball cores also can be made using the materials and processes ofthe invention. To make a golf ball core using RIM polyurethane, the sameprocessing conditions are used as are described above with respect tocovers. One difference is, of course, that no retractor pins are neededin the mold. Furthermore, an undimpled, smaller mold is used. If,however, a one piece ball is desired, a dimpled mold would be used.Polyurethanes also can be used for cores.

Golf balls typically have indicia and/or logos stamped or formedthereon. Such indicia can be applied by printing using a material or asource of energetic particles after the ball core and/or cover have beenreaction-injection-molded according to the present invention. Printedindicia can be formed form a material such as ink, foil (for use in foiltransfer), etc. Indicia printed using a source of energetic particles orradiation can be applied by burning with a laser, burning with heat,directed electrons, or light, phototransformations of, e.g., UV ink,impingement by particles, impingement by electromagnetic radiation etc.Furthermore, the indicia can be applied in the same manner as an in-moldcoating, for example, by applying to the indicia to the surface of themold prior to molding of the cover.

Additional materials may also be added to the boundary layer of thepresent invention as long as they do not substantially reduce theplayability properties of the ball. Such materials include dyes and/oroptical brighteners (for example, Ultramarine Blu™ sold by Whittaker,Clark, and Daniels of South Plainsfield, N.J.) (see U.S. Pat. No.4,679,795); pigments such as titanium dioxide, zinc oxide, bariumsulfate and zinc sulfate; UV absorbers; antioxidants; antistatic agents;and stabilizers. Moreover, the cover compositions of the presentinvention may also contain softening agents such as those disclosed inU.S. Pat. Nos. 5,312,857 and 5,306,760, both of which pertinent partsare hereby incorporated by reference, including plasticizers, metalstearates, processing acids, and the like, and reinforcing materialssuch as glass fibers and inorganic fillers, as long as the desiredproperties produced by the golf ball covers of the invention are notimpaired. The polyurethane which is selected for use as a golf ballcover preferably has a Shore B hardness of 20 to 95, and more preferably30 to 75. The polyurethane which is to be used for a cover layerpreferably has a flex modulus of from about 1 to about 310 kpsi, andmore preferably from about 5 to about 100 kpsi.

Non-limiting examples of suitable RIM systems for use in the presentinvention are Bayflex® elastomeric polyurethane RIM systems, Baydur® GSsolid polyurethane RIM systems, Prism® solid polyurethane RIM systems,all from Bayer Corp. (Pittsburgh, Pa.), SPECTRIM reaction moldablepolyurethane and polyurea systems from Dow Chemical USA (Midland,Mich.), including SPECTRIM MM 373-A (isocyanate) and 373-B (polyol), andElastolit SR systems from BASF (Parsippany, N.J.), and VIBRARIM systemsfrom Crompton Uniroyal Corporation (Middlebury, Conn.). Furtherpreferred examples are polyols, polyamines and isocyanates formed byprocesses for recycling polyurethanes and polyureas. Peroxides, such asMEK-peroxide and dicumyl peroxide can be used. Furthermore, catalysts oractivators such as cobalt octoate 6%, dibutyl tin dilaurate, and thelike, can be used.

The polyurethane prepolymer is preferably a polytetramethylene etherglycol terminated 4,4′-diphenylmethane diisocyanate-based polyurethaneprepolymer. Preferred polytetramethylene ether glycol terminated4,4′-diphenylmethane diisocyanate-based polyurethane prepolymers areavailable from Uniroyal Chemical Company of Middlebury, Connecticut,under the tradename VIBRATHANE®, and include VIBRATHANE® B836,VIBRATHANE® B670, VIBRATHANE® B625. An alternative polyurethaneprepolymer is an ester terminated 4,4′-diphenylmethanediisocyanate-based polyurethane prepolymers such as VIBRATHANE® 8520,VIBRATHANE® 8007, VIBRATHANE® 8010 and VIBRATHANE® 6012.

The ratio of the polyurethane prepolymer to curative is determined bythe nitrogen-carbon-oxygen group (“NCO”) content of the polyurethaneprepolymer. For example, the NCO group content of the polytetramethyleneether glycol terminated 4,4′-diphenylmethane diisocyanate-basedpolyurethane prepolymer is preferably in the range of 12.0% to 18.0%,more preferably in the range of 14.0% to 16.5%, and most preferably16.0%. The NCO content of the ester terminated 4,4′-diphenylmethanediisocyanate-based polyurethane prepolymer is preferably range of 12.0%to 18.0%, more preferably in the range of 14.0% to 16.5%, and mostpreferably 16.0%.

The core 32 of the golf ball 30 is preferably a single solid core suchas disclosed in U.S. Pat. No. 6,612,940, assigned to Callaway GolfCompany and which pertinent parts are hereby incorporated by reference,or such as disclosed in U.S. Pat. No. 6,465,546, also assigned toCallaway Golf Company and which pertinent parts are hereby incorporatedby reference. However, alternative embodiments have a non-solid ormultiple cores such as disclosed in U.S. Pat. No. 6,663,509, whichpertinent parts are hereby incorporated by reference. In a preferredembodiment, the finished core 12 has a diameter of about 1.35 to about1.64 inches for a golf ball 10 having an outer diameter of 1.68 inches.The core weight is preferably maintained in the range of about 32 toabout 40 g. The core PGA compression is preferably maintained in therange of about 50 to 90, and most preferably about 55 to 80.

As used herein, the term “PGA compression” is defined as follows:PGA compression value=180−Riehle compression valueThe Riehle compression value is the amount of deformation of a golf ballin inches under a static load of 200 pounds, multiplied by 1000.Accordingly, for a deformation of 0.095 inches under a load of 200pounds, the Riehle compression value is 95 and the PGA compression valueis 85.

A boundary layer 34 is preferably composed of a thermoplastic material.Suitable thermoplastic materials for the boundary layer 34 include:HYTREL® and/or HYLENE® products from DuPont, Wilmington, Del.; PEBAX®products from Elf Atochem, Philadelphia, Pa.; SURLYN® products fromDuPont; and/or ESCOR® or IOTEK® products from Exxon Chemical, Houston,Tex.

In a preferred embodiment of the golf ball 30, the boundary layer 34comprises a high acid (i.e. greater than 16 weight percent acid) ionomerresin or a blend of one or more high acid ionomers and one or more lowacid ionomers (i.e. 16 weight percent acid or less) The boundary layer34 compositions of the embodiments described herein may include the highacid ionomers such as those developed by E. I. DuPont de Nemours &Company under the SURLYN brand, and by Exxon Corporation under the ESCORor IOTEK brands, or blends thereof. Examples of compositions which maybe used as the boundary layer 34 herein are set forth in detail in U.S.Pat. No. 5,688,869, which is incorporated herein by reference. Theboundary layer 34 high acid ionomer compositions are not limited in anyway to those compositions set forth in said patent. Those compositionsare incorporated herein by way of examples only.

The high acid ionomers which may be suitable for use in formulating theboundary layer 34 compositions are ionic copolymers which are the metal(such as sodium, zinc, magnesium, etc.) salts of the reaction product ofan olefin having from about 2 to 8 carbon atoms and an unsaturatedmonocarboxylic acid having from about 3 to 8 carbon atoms. Preferably,the ionomeric resins are copolymers of ethylene and either acrylic ormethacrylic acid. In some circumstances, an additional comonomer such asan acrylate ester (for example, iso- or n-butylacrylate, etc.) can alsobe included to produce a softer terpolymer. The carboxylic acid groupsof the copolymer are partially neutralized (for example, approximately10-100%, preferably 30-70%) by the metal ions. Each of the high acidionomer resins which may be included in the inner layer covercompositions of the invention contains greater than 16% by weight of acarboxylic acid, preferably from about 17% to about 25% by weight of acarboxylic acid, more preferably from about 18.5% to about 21.5% byweight of a carboxylic acid. Examples of the high acid methacrylic acidbased ionomers found suitable for use in accordance with this inventioninclude, but are not limited to, SURLYN 8220 and 8240 (both formerlyknown as forms of SURLYN AD-8422), SURLYN 9220 (zinc cation), SURLYNSEP-503-1 (zinc cation), and SURLYN SEP-503-2 (magnesium cation).According to DuPont, all of these ionomers contain from about 18.5 toabout 21.5% by weight methacrylic acid. Examples of the high acidacrylic acid based ionomers suitable for use in the present inventionalso include, but are not limited to, the high acid ethylene acrylicacid ionomers produced by Exxon such as Ex 1001, 1002, 959, 960, 989,990, 1003, 1004, 993, and 994. In this regard, ESCOR or IOTEK 959 is asodium ion neutralized ethylene-acrylic neutralized ethylene-acrylicacid copolymer. According to Exxon, IOTEKS 959 and 960 contain fromabout 19.0 to about 21.0% by weight acrylic acid with approximately 30to about 70 percent of the acid groups neutralized with sodium and zincions, respectively.

Furthermore, as a result of the previous development by the assignee ofthis application of a number of high acid ionomers neutralized tovarious extents by several different types of metal cations, such as bymanganese, lithium, potassium, calcium and nickel cations, several highacid ionomers and/or high acid ionomer blends besides sodium, zinc andmagnesium high acid ionomers or ionomer blends are also available forgolf ball cover production. It has been found that these additionalcation neutralized high acid ionomer blends produce boundary layer 34compositions exhibiting enhanced hardness and resilience due tosynergies which occur during processing. Consequently, these metalcation neutralized high acid ionomer resins can be blended to producesubstantially higher C.O.R.'s than those produced by the low acidionomer boundary layer 34 compositions presently commercially available.

More particularly, several metal cation neutralized high acid ionomerresins have been produced by the assignee of this invention byneutralizing, to various extents, high acid copolymers of analpha-olefin and an alpha, beta-unsaturated carboxylic acid with a widevariety of different metal cation salts. This discovery is the subjectmatter of U.S. Pat. No. 5,688,869, which is hereby incorporated byreference. It has been found that numerous metal cation neutralized highacid ionomer resins can be obtained by reacting a high acid copolymer(i.e. a copolymer containing greater than 16% by weight acid, preferablyfrom about 17 to about 25 weight percent acid, and more preferably about20 weight percent acid), with a metal cation salt capable of ionizing orneutralizing the copolymer to the extent desired (for example, fromabout 10% to 90%).

The base copolymer is made up of greater than 16% by weight of an alpha,beta-unsaturated carboxylic acid and an alpha-olefin. Optionally, asoftening comonomer can be included in the copolymer. Generally, thealpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene,and the unsaturated carboxylic acid is a carboxylic acid having fromabout 3 to 8 carbons. Examples of such acids include acrylic acid,methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid,maleic acid, fumaric acid, and itaconic acid, with acrylic acid beingpreferred.

The softening comonomer that can be optionally included in the boundarylayer 34 of the golf ball of the invention may be selected from thegroup consisting of vinyl esters of aliphatic carboxylic acids whereinthe acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkylgroups contain 1 to 10 carbon atoms, and alkyl acrylates ormethacrylates wherein the alkyl group contains 1 to 10 carbon atoms.Suitable softening comonomers include vinyl acetate, methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,butyl methacrylate, or the like.

Consequently, examples of a number of copolymers suitable for use toproduce the high acid ionomers included in the present inventioninclude, but are not limited to, high acid embodiments of anethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer,an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer,an ethylene/methacrylic acid/vinyl acetate copolymer, anethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymerbroadly contains greater than 16% by weight unsaturated carboxylic acid,from about 39 to about 83% by weight ethylene and from 0 to about 40% byweight of a softening comonomer. Preferably, the copolymer containsabout 20% by weight unsaturated carboxylic acid and about 80% by weightethylene. Most preferably, the copolymer contains about 20% acrylic acidwith the remainder being ethylene.

The boundary layer 34 compositions may include the low acid ionomerssuch as those developed and sold by E. I. DuPont de Nemours & Companyunder the SURLYN and by Exxon Corporation under the brands ESCOR andIOTEK, ionomers made in-situ, or blends thereof.

Another embodiment of the boundary layer 34 comprises a non-ionomericthermoplastic material or thermoset material. Suitable non-ionomericmaterials include, but are not limited to, metallocene catalyzedpolyolefins or polyamides, polyamide/ionomer blends, polyphenyleneether/ionomer blends, etc., which preferably have a Shore D hardness ofat least 60 (or a Shore C hardness of at least about 90) and a flexmodulus of greater than about 30,000 psi, preferably greater than about50,000 psi, or other hardness and flex modulus values which arecomparable to the properties of the ionomers described above. Othersuitable materials include but are not limited to, thermoplastic orthermosetting polyurethanes, thermoplastic block polyesters, forexample, a polyester elastomer such as that marketed by DuPont under thebrand HYTREL, or thermoplastic block polyamides, for example, apolyether amide such as that marketed by Elf Atochem S. A. under thebrand PEBEX, a blend of two or more non-ionomeric thermoplasticelastomers, or a blend of one or more ionomers and one or morenon-ionomeric thermoplastic elastomers. These materials can be blendedwith the ionomers described above in order to reduce cost relative tothe use of higher quantities of ionomer.

The Shore D hardness of the boundary layer 34 preferably ranges from 40to 75, as measured according to ASTM D-2290. In a most preferredembodiment, the boundary layer 34 has a Shore D hardness in the range of50-65. One reason for preferring a boundary layer 34 with a Shore Dhardness of 75 or lower is to improve the feel of the resultant golfball. It is also preferred that the boundary layer 34 is composed of ablend of SURLYN® ionomer resins.

One preferred formulation for the boundary layer 34 has 25-50 weightpercent SURLYN 8150, 25-50 weight percent SURLYN 9150, and 25-50 weightpercent SURLYN 6320. Another formulation for the boundary layer 14 has25-75 weight percent SURLYN 9150, and 25-75 weight percent SURLYN 6320.Those skilled in the pertinent art will recognize that other ionomersmay be utilized for the optional boundary layer 34 without departingfrom the scope and spirit of the present invention. The Shore D hardnessof the boundary layer 34 is preferably 50 to 75, more preferably from55-65 Shore D, and most preferably 58-63 Shore D, as measured accordingto ASTM-D2240.

The polyurethane material of the present invention preferably has aShore D hardness ranging from 30 to 60 as measured according toASTM-D2240, more preferably 40 to 55 Shore D, and most preferably 50Shore D.

As shown in FIG. 3, the preferred construction of a golf ball 30utilizing the fast-chemical reaction produced material of the presentinvention is a three-piece solid golf ball having a solid polybutadienecore 32, a boundary layer 34 composed of a blend of ionomers, and acover 36 composed of the polyurethane/polyurea material that istransparent to visible light. The core 32 is preferably compressionmolded, the boundary layer 34 is preferably injection molded, and thecover 16 is reaction injection molded. The golf ball 30 may be finishedwith one or two layers of a clear coating and an optional indicia.

The thickness of the cover 36 preferably ranges from 0.010 inch to 0.070inch, more preferably ranges from 0.014 inch to 0.050 inch, evenpreferably ranges from 0.015 inch to 0.044 inch, most preferably rangesfrom 0.020 inch to 0.030 inch, and is most preferably less than 0.025inch. The boundary layer 34 is preferably injection molded andpreferably ranges in thickness from 0.040 inch to 0.090 inch, morepreferably from 0.045 inch to 0.070 inch, and most preferably from 0.050inch to 0.060 inch. The boundary layer 34 may also be compression moldedfrom half shells. The core 32 preferably has a diameter of between 1.35inches and 1.60 inches, more preferably between 1.45 inches and 1.55inches, and most preferably 1.49 inches. The core 32 preferably has aPGA compression ranging from 40-110 points, and most preferably 80points. A more detailed description of a construction and performanceproperties of a golf ball utilizing the polyurethane material of thepresent invention is set forth in U.S. Pat. No. 6,443,858, for a GolfBall With A High Coefficient Of Restitution, issued on Sept. 2, 2002,assigned to Callaway Golf Company, and U.S. Pat. No. 6,478,697 for aGolf Ball With A High Coefficient Of Restitution, filed on Nov. 12,2002, assigned to Callaway Golf Company, both of which are herebyincorporated by reference in their entireties.

The Shore D hardness of each of the golf balls 10, 20 and 30, asmeasured on the golf ball, is preferably between 30 Shore D points to 75Shore D points, and most preferably between 50 Shore D points and 65Shore D points. The hardness is measured using an Instron Shore DHardness measurement device wherein the golf ball is placed within aholder and the pin is lowered to the surface to measure the hardness.The average of five measurements is used in calculating the ballhardness. The ball hardness is preferably measured on a land area of thecover 14, 24 and 36. The preferred overall diameter of the golf ball 10,20 or 30 is approximately 1.68 inches, and the preferred mass isapproximately 45.5 grams. However, those skilled in the pertinent artwill recognize that the diameter of the golf ball 10, 20 or 30 may besmaller (e.g. 1.65 inches) or larger (e.g. 1.70 inches) withoutdeparting from the scope and spirit of the present invention. Further,the mass may also vary without departing from the scope and spirit ofthe present invention.

The surface geometry of each of the golf balls 10, 20 and 30 ispreferably a conventional dimple pattern such as disclosed in U.S. Pat.No. 6,213,898 for a Golf Ball With An Aerodynamic Surface On APolyurethane Cover, which pertinent parts are hereby incorporated byreference. Alternatively, the surface geometry of each of the golf balls10, 20 and 30 may have a non-dimple pattern such as disclosed in U.S.Pat. No. 6,290,615 for A Golf Ball Having Tubular Lattice Pattern, orco-pending U.S. patent application Ser. No. 10/709,018, filed on Apr. 7,2004 for an Aerodynamic Surface Geometry Of A Golf Ball, both of whichpertinent parts are hereby incorporated by reference.

EXAMPLES

The following examples are included for purposes of illustration and arenot intended to be limiting.

Example 1

Golf balls having cores and covers were produced using various aliphaticand aromatic polyurethane RIM systems. The aliphatic RIM systemscomprised an aliphatic polyol and an H₁₂MDI/PTMEG prepolymer. Thearomatic systems comprised MDI/PTMEG-based prepolymers and PTMEG/MOCAcuratives. (Note: MOCA is 4,4′-methylene-bis-(ortho-chloroaniline, acuring agent for polyurethane elastomers.) The balls were tested tomeasure light stability, cut, scuff and Shore C and Shore D hardness.Two controls, a STRATA® TOUR ULTIMATE ball and a TITLEIST® PROV1™ ballwere also measured. The results follow in Table 2.

TABLE 1 Shore Weather Type Scuff Cut Oven C, D Test Aromatic SystemControl 1.6 2 Above 46, Fail Aromatic Ave. 34 Harder 1.8 2 Above 40,Fail Ave. 29 Harder, 1.7 2 Above 40, Fail more Ave. 28 resilientAliphatic System Control 1.8 2 Above 52, Pass Aliphatic Ave. 34 Harder2.0 2 Above 50, Pass Ave. 33 Harder, 2.0 2 Above 61, Pass more Ave. 39resilient Controls Type Scuff Cut Oven Weather Test Tour Ultimate 3.0 3Good Pass ProV1 2.0 1 Excellent Pass

Table 1 shows that golf ball covers made with aliphatic RIM systems haveproperties similar to those of aromatic RIM systems as well asthermoplastic polyurethanes and cast polyurethanes, as exhibited by thecommercially available samples. The aliphatic RIM covers passed theweather test as well.

Example 2

Additional two-piece and three-piece golf balls having were producedusing various aliphatic and aromatic polyurethane RIM systems. Thealiphatic RIM systems comprised an aliphatic polyol and an H₁₂MDI/PTMEGprepolymer. The aromatic systems comprised MDI/PTMEG-based prepolymersand PTMEG/MOCA curatives. The balls were tested to measure lightstability, cut, scuff and Shore C hardness. Two controls, a STRATA® TOURULTIMATE ball and a TITLEIST® PROV1™ ball were also measured. Theresults follow in Table 3.

TABLE 2 Weather Type Scuff Cut Oven Shore C Test Aromatic System 3 piece2.5 2 Good 72 Fail 3 piece 3.0 1 Good 64 Fail 3 piece 3.3 1 Good 75 FailAliphatic System 2 piece 1.7 1 Exc. 67 Pass 3 piece 1.7 2 Exc. 69 Pass 3piece 2.0 2 Exc. 75 Pass 3 piece 2.3 1 Exc. 69 Pass Controls Type ScuffCut Oven Weather Test Tour Ultimate 3.0 3 Good Pass ProV1 3.1 2Excellent Pass RIM 3.1 2 Excellent Pass

The above results in Table 2 also show that the golf balls having a RIMpolyurethane cover formed from an aliphatic based polyurethane/polyureaexhibited scuff and cut results as good as commercially available golfballs and aromatic based polyurethane/polyurea covered golf balls.Additionally, the golf balls of the invention having aliphatic basedpolyurethane/polyurea covers exhibited better light stability asexhibited by the weather test.

In a particularly preferred form of the invention, at least one layer ofthe golf ball contains at least one part by weight of a filler. Fillerspreferably are used to adjust the density, flex modulus, mold release,and/or melt flow index of a layer. More preferably, at least when thefiller is for adjustment of density or flex modulus of a layer, it ispresent in an amount of at least 2 parts by weight based upon 100 partsby weight of the layer composition. With some fillers, up to about 200parts by weight probably can be used.

A density adjusting filler according to the invention preferably is afiller which has a specific gravity which is at least 0.05 and morepreferably at least 0.1 higher or lower than the specific gravity of thelayer composition. Particularly preferred density adjusting fillers havespecific gravities which are higher than the specific gravity of theresin composition by 0.2 or more, even more preferably by 2.0 or more.

A flex modulus adjusting filler according to the invention is a fillerwhich, when used in an amount of from about 1 to about 100 parts byweight based upon 100 parts by weight of resin composition, will raiseor lower the flex modulus (ASTM D-790) of the resin composition by atleast 1% and preferably at least 5% as compared to the flex modulus ofthe resin composition without the inclusion of the flex modulusadjusting filler. A mold release adjusting filler is a filler whichallows for the easier removal of a part from a mold, and eliminates orreduces the need for external release agents which otherwise could beapplied to the mold. A mold release adjusting filler typically is usedin an amount of up to about 2 weight percent based upon the total weightof the layer.

A melt flow index adjusting filler is a filler which increases ordecreases the melt flow, or ease of processing of the composition.

The layers may contain coupling agents that increase adhesion ofmaterials within a particular layer e.g. to couple a filler to a resincomposition, or between adjacent layers. Non-limiting examples ofcoupling agents include titanates, zirconates and silanes. Couplingagents typically are used in amounts of from about 0.1 to about 2 weightpercent based upon the total weight of the composition in which thecoupling agent is included.

A density adjusting filler is used to control the moment of inertia, andthus the initial spin rate of the ball and spin decay. The addition inone or more layers, and particularly in the outer cover layer of afiller with a lower specific gravity than the resin composition resultsin a decrease in moment of inertia and a higher initial spin rate thanwould result if no filler were used. The addition in one or more of thecover layers, and particularly in the outer cover layer of a filler witha higher specific gravity than the resin composition, results in anincrease in moment of inertia and a lower initial spin rate. Highspecific gravity fillers are preferred as less volume is used to achievethe desired inner cover total weight. Nonreinforcing fillers are alsopreferred as they have minimal effect on COR. Preferably, the fillerdoes not chemically react with the resin composition to a substantialdegree, although some reaction may occur when, for example, zinc oxideis used in a shell layer which contains some ionomer.

The density-increasing fillers for use in the invention preferably havea specific gravity in the range of from about 1.0 to about 20. Thedensity-reducing fillers for use in the invention preferably have aspecific gravity of from about 0.06 to about 1.4, and more preferablyform about 0.06 to about 0.90. The flex modulus increasing fillers havea reinforcing or stiffening effect due to their morphology, theirinteraction with the resin, or their inherent physical properties. Theflex modulus reducing fillers have an opposite effect due to theirrelatively flexible properties compared to the matrix resin. The meltflow index increasing fillers have a flow enhancing effect due to theirrelatively high melt flow versus the matrix. The melt flow indexdecreasing fillers have an opposite effect due to their relatively lowmelt flow index versus the matrix.

Fillers which may be employed in layers other than the outer cover layermay be or are typically in a finely divided form, for example, in a sizegenerally less than about 20 mesh, preferably less than about 100 meshU.S. standard size, except for fibers and flock, which are generallyelongated. Flock and fiber sizes should be small enough to facilitateprocessing. Filler particle size will depend upon desired effect, cost,ease of addition, and dusting considerations. Examples of fillerssuitable for use include, but are not limited to, precipitated hydratedsilica, clay, talc, asbestos, glass fibers, aramid fibers, mica, calciummetasilicate, barium sulfate, zinc sulfide, lithopone, silicates,silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates,metals, metal alloys, tungsten carbide, metal oxides, metal stearates,particulate carbonaceous materials, micro balloons, and combinationsthereof. All of fillers except for metal stearates would be expected toreduce the melt flow index of an injection molded cover layer. Theamount of filler employed is primarily a function of weight requirementsand distribution.

Scuff Resistance

The scuff resistance test was conducted in the manner described below.The balls that were tested were primed and top coated. A Titleist Vokey56° Wedge (256·12) was mounted in a mechanical swing machine. The clubswing speed used is 70 mph. After each hit, the clubface is brushedclean using a nylon bristled brush. A minimum of three samples of eachball were tested. Each ball was hit three times at three differentlocations so as not to overlap with other strikes. The details of theclub face are critical, and are as follows:

Groove width—0.026 inches

Groove depth—0.014 inches;

For each strike, a point value is assigned based on a scale from 0.0 to6.0 with 0.0 representing no visible mark from the strike and 6.0representing shredding of the material, with consideration given to apotential end user's perception of cover damage. After completing allstrikes, determine the average point value. This average point value, orrank, can be correlated to the chart below.Scuff Test Ranking

Rank Average Point Value Excellent 0.0-1.0 Very Good 1.1-2.0 Good2.1-3.0 Fair 3.1-4.0 Borderline 4.1-5.0 Poor (unacceptable) 5.1-6.0Cut Test

The cut test (off center cut) was performed as described below. An offcenter cut test was used as it more closely represents actual play. Theshear component of this blow makes the off-center cut test the mostsevere and most useful in determining the cut resistance of a covermaterial.

The cut performance test consists of cutting a minimum of three golfballs at least twice. Each cut is in a different location on the ball soas not to overlap other cuts. Cutting the samples directly on theequator should be avoided. The off-center cut test uses a guillotine tostrike the ball with a glancing blow and represents a mishit where theball might be topped or skulled. To perform the test, adjust the sampleholder to the appropriate position and place the golf ball in the sampleholder. Carefully lift the guillotine to the top of its stroke, makingsure not to hit the release switch on the left of the head. The headshould stay at the top by means of its clutch mechanism. Tap the releaseswitch on the left of the head to release the guillotine to strike theball. Rotate the ball for the next blow(s) making sure the subsequentstrike(s) will not overlap. Once all the samples have been cut, eachstrike is ranked according to the guidelines below. The cut ranking forthe sample set is represented by the average of all cuts. An overallranking of 3 or better is necessary for acceptable field durability.

DEFECT CHARACTER CUT RANK No Visible Marks 0 Barely Visible Lines 1Distinct Lines 2 Lines with few Wrinkles 3 Wrinkles and Minor Cuts 4Deep Cuts or Tearing 5Weather Test

Golf balls are placed in a weatherometer, such as an Atlas Ci35A, 6500watt weatherometer, for 36 hours (exposure of approximately 0.65watts/square meter). They are exposed to constant light for the durationof the test. After 36 hours, the golf balls are removed and the coversare checked for light stability. If there is significant color change,the ball fails.

Oven Aging Test

Golf balls were placed in an oven at about 70 degrees Celsius overnight(approximately 16 hours). At the end of the test, the golf balls wereremoved and visually assessed to determine if the cover “melted” or not.The covers were rated as Excellent, Good, or Poor, depending on how muchthe cover melted or changed.

From the foregoing it is believed that those skilled in the pertinentart will recognize the meritorious advancement of this invention andwill readily understand that while the present invention has beendescribed in association with a preferred embodiment thereof, and otherembodiments illustrated in the accompanying drawings, numerous changes,modifications and substitutions of equivalents may be made thereinwithout departing from the spirit and scope of this invention which isintended to be unlimited by the foregoing except as may appear in thefollowing appended claims. Therefore, the embodiments of the inventionin which an exclusive property or privilege is claimed are defined inthe following appended claims.

1. A golf ball comprising: a core comprising a polybutadiene mixture; aboundary layer formed over the core, the boundary layer having anindicia printed on a surface of the boundary layer; and a cover formedover the boundary layer, the cover having a thickness ranging from 0.015inch to 0.044 inch, a Shore B hardness ranging from 20 to 95 and a flexmodulus ranging from 5 kpsi to 100 kpsi, the cover composed of a fastchemical reaction aliphatic polyurethane material formed from reactantscomprising 1,6, hexamethylene-diisocyanate and a polytetramethyleneether glycol; wherein the cover material is transparent to visible lightand the indicia printed on the surface of the boundary layer is visible.